Core B is responsible for confirming all cancer reports and all deaths in the Nurses' Health Study cohort. The specific aims for this core are as follows: 1) To document and confirm reports of incident cancer as collected from the questionnaires, telephone interviews, and death records. 2) To identify all deaths among cohort participants and to ascertain the cause of death. 3) To provide standardized data files of cancer diagnoses and all deaths for epidemiologic analyses. Under the direction of Meir Stampfer, MD, DrPh, Core B obtains medical records and other relevant information to confirm cancer diagnoses and cohort deaths. The trust that has evolved over the past thirty-two years between the NHS investigators and cohort participants has led to an extremely high degree of cooperation in securing permission to review medical records, and from the families in ascertaining the details of the cause of death. Medical records are reviewed by physicians according to uniform standardized criteria to confirm the cancer diagnoses and obtain details of the histopathology, including tumor site, stage, and grade. We learn of most deaths through the questionnaire mailings and we search the National Death Index for questionnaire nonrespondents. State tumor registries are also utilized to confirm cancer diagnoses and deaths. Custom-designed computer software has been developed to track the progress from the initial report of a diagnosis or death to the final confirmation. The software also automatically generates letters to participants and medical institutions for requesting medical records and additional Information. At the end of every biennial follow-up cycle, standardized files are generated for specific cancer diagnoses and for all deaths to be used by all investigators conducting research with the NHS data.